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Fast neutron detectors with silicon photomultiplier readouts
摘要： This work summarizes a fast neutron detection performance of two different silicon photomultipliers from two manufacturers. The first SiPM (MAPD-3NK) from Zecotek Photonics consists of deeply buried cells with the active area 3.7x3.7 mm2. The second one (MPPC-S12572-010P) from Hamamatsu, however, consists of surface cell structure which the active area is 3x3 mm2. Both SiPMs have the same pixel density of 10000 mm-2. Both SiPMs coupled to Stilbene (5*5*5 mm3) and p-terphenyl (5*5*5 mm3) plastic scintillators were evaluated for detection ability of fast neutrons using a PuBe neutron source. Charge comparison and zero crossing neutron/gamma discrimination techniques were performed for these detectors and the results were compared. The obtained results prove a good fast neutron detection performance of the SiPMs which makes it possible to use these types of neutron detectors in fast neutron detection applications.
关键词： Pulse shape discrimination,Micropixel avalanche photodiode,Charge comparison,SiPM,MAPD,PSD,Zero crossing,Silicon photomultiplier
更新于2025-09-23 15:21:21
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[IEEE 2017 IEEE 7th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems (CYBER) - Honolulu, HI, USA (2017.7.31-2017.8.4)] 2017 IEEE 7th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems (CYBER) - Modeling and Stability Analysis of Robot Calibration System Based on Dual PSD
摘要： Industrial robot repeat positioning accuracy is high, but the absolute positioning accuracy is low, which greatly affects the application of offline programming. Compared with the traditional method, calibration method based on dual-PSD provides more efficient way for improving absolute positioning accuracy of robot. However, the required alignment of laser beam to shoot at the two PSD centers was performed separately, which required to pre-known some parameters for the alignment task. This paper proposes a simultaneous laser beam alignment method without knowing these parameters to perform the laser beam alignment task. In this paper, the motion of the end-effector is divided into translational motion and rotational motion. By designing translational motion and rotational motion controller of the robot end-effector respectively, the unknown parameters in the model are estimated, and the laser spot is alligned with the double PSD at the same time. Stability analysis.
关键词： calibration,industrial robot,dual PSD
更新于2025-09-23 15:21:21
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Research and design of low-power grid-connected PV power generation system based on automatic solar tracking
摘要： A low-power grid-connected photovoltaic (PV) power generation system based on automatic solar tracking is designed in this paper. In order to increase the level of accuracy of automatic solar tracking, the part of automatic solar tracking adopts the method of hybrid tracking and uses pin-cushion two-dimensional position sensitive detector plus four silicon PV cells as the photosensitive element. An adaptive topological structure of the main circuit based on a cascaded Boost converter circuit and the H6-type inverter topology are designed for the system to obtain a better working condition. Then an MPPT algorithm combined modified constant voltage algorithm with modified variable step-size increment conductance algorithm is proposed in order to improve the efficiency of PV power generation. The experimental results showed the effectiveness of the control system. Finally, the hardware and software of the system are also designed. Moreover, a graphic interface made with the LabVIEW software allows the user to monitor and save the data in a file.
关键词： Automatic solar tracking,human–computer interaction,H6-type inverter topology,pin-cushion PSD,PV grid-connected,MPPT
更新于2025-09-19 17:15:36
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Thermal Noise in Optically Pumped DF-VECSELs
摘要： Over the last decades, the low noise properties of Vertical–External–Cavity Surface–Emitting Lasers (VECSELs) have aroused interest for various applications. The dual–frequency (DF) VECSELs can generate a very low noise RF signal resulting from the beatnote of two orthogonal linear polarizations as sketched in Fig.1(a). For example, the very high spectral purity and class–A operation of DF–VECSELs are of interest for ultrastable atomic clocks [1] or microwave electronics for optically-carried RF signal processing or wide-band RADARs. The sources of noise of optically pumped VECSELs are well identi?ed : (i) the intensity noise induced by the pump through the laser dynamics, (ii) the spontaneous emission contribution, (iii) technical noises such as mechanical vibrations, and (iv) the thermal noise. The two ?rst sources of noise are well modeled and understood. But in [2] a simple second–order low-pass ?lter behaviour is assumed for the thermal contribution to the frequency noise power spectral density (PSD) spectra. Yet, de?ning unequivocally a cut–off frequency is not obvious since different time scales are actually involved. Moreover, this over–simpli?ed model fails at low frequencies in [3] as displayed in Fig.1(b). Indeed, below 200 kHz the slope of the beatnote phase–noise spectrum of a DF–VECSEL at 852 nm obeys a f ?3 scaling law instead of the f ?4 expected behaviour. The aim of the present work is to microscopically model the thermal noise contribution. First, we describe the layers of the optically pumped emitting–surface, which is glued to a Peltier cooler. The heat equations take into account transverse and longitudinal diffusion processes. Assuming a gaussian pro?le for the pump, we obtain the temperature ?eld inside the structure using Hankel transformation formalism and we investigate the transient thermal response. The pump intensity ?uctuations induce heat ?uctuations inside the structure leading to changes of the refractive index and the material thermal–expansion, which are responsible for frequency ?uctuations of the laser mode. We ?nd an analytical expression of the frequency noise PSD induced by these thermo-optic effects, which allows to model the beatnote phase noise PSD of DF-VECSELs. We ?nd a very good agreement with the f ?3 slope of the experimental datas and we evidence the fundamental thermal ?uctuations contribution at room temperature. Such thermodynamics ?uctuations were already investigated for VCSEL structures in [4], starting from a stochastic heat equation. We extend it to a full study of the frequency noise PSD spectrum for DF-VECSELs. We obtain a fully analytical expression and discuss its validity.
关键词： Thermal noise,frequency noise PSD,thermal fluctuations,optically pumped,DF-VECSELs
更新于2025-09-16 10:30:52
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[IEEE 2019 International Conference on Indoor Positioning and Indoor Navigation (IPIN) - Pisa, Italy (2019.9.30-2019.10.3)] 2019 International Conference on Indoor Positioning and Indoor Navigation (IPIN) - Indoor Positioning System Based on LED lighting and PSD Sensor
摘要： This paper shows a system and a method for indoor positioning based on the LED lighting installed on the environment. The proposal is based on the modulation of the visible light signal emitted in frequencies ranging from 50 to 200 kHz and detection by means of a PSD (Position Sensitive Detector) photodiode. The paper describes the mathematical modelisation of the proposed Indoor Positioning System (IPS), considering that the detector will move on a planar surface. Several synthetic results are shown for distances of 1 and 3 meters between the light source and detector. The positioning technique is based on the angle of arrival (AoA) captured from the LED lighting. Using genetic algorithm, we have obtained the model parameters for the detector (composed of a PSD and coupled lens). Different experimental tests have been carried out to determine the precision in positioning with the proposed system, considering a ceil lighting at 3 meters distance, with a coverage surface area of 3x3 m2. The average error results in the positioning of the detector, with low multipath (MP) effect, are below 1 cm in 80% of the tested points. Considering the presence of strong effects of multipath signals, the maximum positioning error remains below 4.5 cm.
关键词： Visible light positioning - VLP-,Indoor positioning,Positioning sensor device -PSD-,Angle of Arrival -AoA-
更新于2025-09-12 10:27:22
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[IEEE 2018 International Conference on Indoor Positioning and Indoor Navigation (IPIN) - Nantes, France (2018.9.24-2018.9.27)] 2018 International Conference on Indoor Positioning and Indoor Navigation (IPIN) - Simplified Calibration Process for a PSD-Based Optical IPS
摘要： Indoor Positioning Systems (IPS) usually require a calibration process to obtain precise measurements. In the case of systems with optical components, calibration may be time-consuming and requires a specific infrastructure. In this paper, we present a model and a calibration method for an optical sensor based on Direct Linear Transformation (DLT), which directly obtains the transformation between the sensor surface and the surface of the moving agent. Our method provides results similar to those that would be obtained with an optimal calibration, with differences of only are few mm.
关键词： Optical Signal,Infrared,Transformation,PSD sensor,Indoor Positioning Systems
更新于2025-09-09 09:28:46
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Materials Science and Technology of Optical Fabrication || Surface Roughness
摘要： Because it influences optical-scatter losses and downstream laser modulation [1], the surface roughness of an optical-glass component is an important parameter for many optical systems (including lasers and telescopes). During optical polishing, a number of interactions between the workpiece, polishing slurry, and pad may influence the resulting workpiece roughness at different spatial scale lengths. The phenomena affecting large spatial scale length (>1 mm) on the workpiece (i.e. surface figure) are described in Chapter 2 (see Figure 2.1). By contrast, in this chapter, the phenomena and process parameters affecting short spatial scale lengths (<1 mm) (i.e., surface roughness from AFM2 scale roughness to μ-roughness) are described (see Figure 1.8). Fine-scale roughness, typically measured by atomic force microscopy (AFM), is referred to as AFM1 (≤5 μm) and AFM2 roughness (≤50 μm), as represented on the right of the plot. Roughness at this scale is influenced by parameters such as the single-particle removal function, Beilby layer properties, slurry particle size distribution (PSD), pad topography, pad mechanical properties, and slurry particle redeposition. The next higher spatial scale length (the micrometer to millimeter range, known as micro- or μ-roughness), is usually measured by white-light interferometry (Figure 1.8). μ-Roughness is affected not only by the smaller spatial-scale length phenomena given above, but also by factors governing slurry-interface interactions, such as the spatial distribution of slurry particles present at the interface. These parameters and phenomena are listed Figure 4.1, consisting of a schematic of the workpiece–lap interface at the spatial scale length of interest that influences the final polished surface roughness. Figure 4.1 provides a valuable outline for this chapter.
关键词： Optical Polishing,Slurry PSD,Pad Topography,AFM,μ-Roughness,Surface Roughness
更新于2025-09-04 15:30:14